1. Field of the Invention
This invention relates to a process, apparatus and system for forming a sterile connection (sterile docking) between two tubes.
At the present time there are a number of medical and scientific procedures which require the sterile transfer of fluids from one container to another. The only truly sterile transfer system in current commercial use involves prejoining containers with tubes and then sterilizing the entire assembly. This is inflexible and costly since new containers cannot be added and the number of joined containers needed is often not known at the time of initial filling.
An example of the need for sterile docking is in continuous ambulatory peritoneal dialysis (CAPD). This procedure is replacing dialysis of blood outside the body in membrane diffusion cells where waste products normally removed by kidneys are washed from the blood, which is then returned to the patient. Dialysis outside of the body is a time-consuming procedure and sometimes results in damage to the blood by exposure to materials and conditions external to the body. In CAPD, the patient is required to spend time only for draining spent dialysate and replacing it with a fresh solution.
The CAPD patient has a tube connected to his or her peritoneal cavity via an implanted catheter. A tube from a bag of fresh dialysis solution is connected to the patient's tube. The fresh dialysis solution is drained from the bag into the patient's peritoneal cavity where it remains for about 3-4 hours. During this treatment period, the empty bag is folded and carried by the patient who can continue with his or her normal activities. After this treatment period, the spent dialysate is drained back into the empty bag which is then disconnected from the patient's tube. A bag of fresh dialysis solution is then connected to the patient's tube and the procedure is repeated. Connection to a new bag of dialysis solution exposes the tube ends to airborne bacteria or other contamination even though precautions are taken. Prior to the invention disclosed in U.S. Pat. No. 4,369,779, no satisfactory way has existed to insure sterility in spite of the elaborate and costly precautions employed including the use of masks, gloves, gauze strips and disinfectant solutions. Usually with methods now commercially available contamination occurs to the extent that a case of peritonitis is contracted perhaps on the average once or more a year and scar tissue from it inhibits dialysis.
Truly sterile connections could minimize the occurrence of peritonitis. Also any other treatment bags, such as for an antibiotic, bacteriostat, or other medication, could be connected as desired.
A similar need for sterile connection exists for blood bags. At present, blood from a donor is drawn into a primary bag which may be joined to one or two satellite bags, all connected and sterilized before use. These satellite bags may be needed for holding blood separated components, such as plasma or platelets; treating agents, such as bases, buffers, stabilizers for cell metabolism, other preservatives, or rejuvenants; or washes to remove a treating agent or other contaminant. Actually, it is not feasible to have preconnected bags for all the treatments which may be desired. Prior to the invention disclosed in U.S. Pat. No. 4,369,779, supplemental treatments such as fresh preservative could not be added sterilely during bag storage by any commercially acceptable procedure. In addition, to avoid the expense of unused satellite bags, the number of such bags is chosen based on limited, predicted needs. The inability to forecast needs well adds greatly to inventory requirements and complicates scheduling of blood donations.
Currently, very limited use is made of quality control as a time assay of the quantity and quality of components in separated blood factions. The main reason for the current limited use is that heretofore, using methods commercially available, any entry into a sterile blood unit exposed the blood to bacteria, thereby requiring that the blood be used within 24 hours from entry. Hence, although the viability of stored blood components can be extended by supplemental treatments, such as adding a preservative during storage, such treatments are usually not effected.
Moreover, the primary blood bag contains anticoagulant which can be sterilized only by heat (steam); thus all preconnected bags are also sterilized by wet-sterilization techniques, i.e., steam or hot water in an autoclave apparatus. These bags are made of plasticized polyvinyl chloride (PVC), although other materials are known to be useful for constructing bags which are favorable for other reasons, such as greater oxygen permeability. Since many such materials, e.g., oxygen permeable polyethylene, are not steam sterilizable, they are not now used in preconnected systems.
A sterile connection means would permit one to effect whatever processing is desired without compromising sterility, limiting storage life or requiring the preconnection of a multitude of bags, all wet-sterilizable, without knowing which, if any, will be used.
2. References
U.S. Pat. No. 3,013,925, issued to Larsen on Dec. 19, 1961, discloses a method of welding two joints of thermoplastic pipe wherein the inside of each end of the joints of pipe to be welded is beveled and the ends of the pipes are heated, for example by pressing the ends of the sections of pipe against a heated plate, after which the ends of the sections are forced together so that flow of softened material is to the outside of the pipe and a weld is effected substantially without formation of a bead on the inside of the welded pipe.
U.S. Pat. No. 3,035,631, issued to Knowles on May 22, 1962, discloses a tip for welding plastic parts. The tip has a knife edge at each of two opposing ends. One end of the knife is thick whereas the other is thin. The patent states that as the thin end passes through the joint, it will induce molten plastic surfaces to flow together.
U.S. Pat. No. 3,117,903, issued to Hix on Jan. 14, 1964, discloses a method of joining thermoplastic pipe without forming a troublesome inside ridge at the point of weld. The ends of the pipe to be welded are immersed in a hot bath of an inert high boiling organic liquid to cause the ends to expand and flare outwardly so that when the pipe is withdrawn from the bath and the ends butted together, the polymer in the two sections of pipe fuses together without forming a troublesome ridge.
U.S. Pat. No. 3,897,296, issued to Waldrum on July 29, 1975, discloses a method of welding two plastic surfaces together by juxtapositioning the surfaces, heating the surfaces to a temperature approaching the flash point of the plastic surfaces to liquefy the surfaces, removing a portion of the liquefied surfaces to expose unoxidized surfaces therebeneath and immediately bringing the unoxidized surfaces into abutment with one another. The patent is silent as to cutting a tube as well as forming a sterile dock.
U.S. Pat. No. 3,968,195, issued to Bishop on July 6, 1976, discloses a method for making a sterile connection between two rigid tubes the free ends of which have thermoplastic diaphragms which seal off the free ends. When a sterile connection between the free ends of the two tubes is desired, the free ends of each rigid tube are aligned while being spaced slightly apart, and each thermoplastic diaphragm is opened by heating. The free ends of the rigid tubes are then brought into contact and held in position under a slight pressure while the thermoplastic material cools and solidifies, thereby creating a permanent connection. This process requires tubes which have low-melting thermoplastic diaphragms on the ends which can only be used once, i.e., another connection to the same tubing cannot be made.
U.S. Pat. No. 4,209,013, issued to Alexander et al. on June 24, 1980, discloses an improvement in a sterile connector system for continuous peritoneal dialysis in which a dialysis solution container having a transfer port is coupled to tubing extending from a patient's peritoneal cavity. The improvement comprises a flexible housing having a first area thereof for attachment to the transfer port and a second spaced area for attachment to the patient's tubing. The attachment areas define openings for enabling the transfer port and patient's tubing to extend within the interior of the flexible housing when they are attached thereto. The flexible housing has means for receiving a sterilizing fluid therein and is operable to enable the transfer port and the patient's tubing to be sterilized within the housing and also connected to each other within the housing.
U.S. Pat. No. 4,223,675, issued to Williams on Sept. 23, 1980, discloses a system for producing sterile, nonautoclavable body fluid containers having autoclaved liquid therein, comprising a dry-sterilized package formed of a material which is unsuitable for being subjected to autoclave conditions, said dry-sterilized package including a sterile communication with the interior of said package; an autoclavable dispenser constructed of an autoclavable substance and containing liquid which was sterilized within the dispenser, said dispenser including a sterile connector having an initially closed sterile aperture in sterile communication with the interior of the dispenser; said package sterile connector and said dispenser sterile connector being in mating engagement with each other.
U.S. Pat. No. 4,242,310, issued to Greff et al. on Dec. 30, 1980, discloses a sterile connection apparatus for enabling the connection of a first tube to a transfer tube of a medical solution container. The apparatus comprises a housing including a base portion and a cover portion adapted for interfitting with each other to provide a substantially closed interior volume. The housing includes means for receiving the first tube and means for receiving the transfer tube from a medical solution container. The housing carries means which are located within the housing and operable from outside the housing for enabling manipulation of one of the tubes with respect to the other tube. Means are provided for sterilizing the tube portions within the substantially closed interior volume.
"An Aseptic Fluid Transfer System for Blood and Blood Components", B. A. Myhre et al., Transfusion, Vol. 18, No. 5, pp. 546-552, September-October 1978, discloses a process for heat sealing two aseptic fluid transfer system (AFTS) units together. The AFTS units contain a layer of Kapton.RTM. film (an aromatic polyimide resin which is stable at relatively high temperatures). A pair of dies, one of which is flat and one of which has a raised "H" shaped area, are brought together under a pressure of 100 psi (6.9.times.10.sup.6 dynes per square centimeter) with the AFTS units disposed between the dies. The temperature of the dies is raised to 200.degree. C. (392.degree. F.) over a period of 45 seconds. The dies are withdrawn and upon removal of the AFTS units from the dies, the AFTS units are heat sealed together by a seal surrounding an opening between the AFTS units. Blood bags constructed with an AFTS unit attached can thereby be joined. This system is slow and requires specially constructed units that can only be used once.
German OS No. 2,250,130 discloses a process and apparatus for bonding plastic parts by welding. The process is characterized in that the two plastic parts to be bonded to each other are pressed to a heating element introduced between the two parts; the areas of the plastic parts adjoining the heating element are surface melted by a very short and a very high temperature effect; and then, while maintaining the pressure exerted on the plastic parts, the heating element is withdrawn from the plastic parts and the two parts are immediately pressed together. The German publication does not mention plastic tubing nor how to make a sterile connection between two closed-end tubes.
U.S. Pat. No. 4,369,779, issued to Spencer on Jan. 25, 1983, discloses a process, apparatus and system for sterilely connecting two sterile, closed end tubes. The process comprises urging a hot cutting means through each tube and simultaneously forming a continuous molten seal between a heated cutting surface and a transverse section of each said tube thereby maintaining a seal between the interior and exterior of the tubes, aligning the tubes with each other and joining the respective molten ends of the tubes together to form a joint between the tubes, both while maintaining said seal.
This patent discloses an apparatus comprising a cutting means, means adapted to heat said cutting means, a pair of mounting blocks adapted to receive and hold two tubes to be joined, means to provide movement between said blocks and said cutting means to a position such that the cutting means is between said blocks and traversing where the blocks are adapted to receive tubes, means adapted to realign said blocks to a position where two different tube ends are aligned with and facing each other, and means to separate said blocks and the cutting means while urging the blocks together. The patent teaches that during the connection operation there should be no significant visible deformation of the tubes and that, in order to obtain a secure dock, the tubes to be joined must not contain more liquid than a thin film on the walls at or near the locations where they are to be cut and joined.
When using the process of this patent, it is necessary to express liquid from the tubes prior to sterile connection or at least to effect sterile connection at a portion of the tubing having an air gap of 13-25 mm (0.5 to 1 inch). There is a need for a sterile docking process which would provide sterile connection of liquid filled tubes thereby effecting a strong joint without introducing contamination or decomposition of the liquid. This is particularly true where a suitable air gap does not exist or is not desirable. There is also a need for such a process which provides total containment of the fluid within the tubes.